/*
* To remove a leaf_node:
* Search to the tree location appropriate for the given leaf_node's key:
* - If location does not hold a matching entry, abort and do nothing.
* - Replace the matching leaf_node with a NULL entry (and free the leaf_node).
* - Consolidate int_nodes repeatedly, while walking up the tree towards root.
*/
static void note_tree_remove(struct notes_tree *t, struct int_node *tree,
unsigned char n, struct leaf_node *entry)
{
struct leaf_node *l;
struct int_node *parent_stack[20];
unsigned char i, j;
void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
if (GET_PTR_TYPE(*p) != PTR_TYPE_NOTE)
return; /* type mismatch, nothing to remove */
l = (struct leaf_node *) CLR_PTR_TYPE(*p);
if (hashcmp(l->key_sha1, entry->key_sha1))
return; /* key mismatch, nothing to remove */
/* we have found a matching entry */
free(l);
*p = SET_PTR_TYPE(NULL, PTR_TYPE_NULL);
/* consolidate this tree level, and parent levels, if possible */
if (!n)
return; /* cannot consolidate top level */
/* first, build stack of ancestors between root and current node */
parent_stack[0] = t->root;
for (i = 0; i < n; i++) {
j = GET_NIBBLE(i, entry->key_sha1);
parent_stack[i + 1] = CLR_PTR_TYPE(parent_stack[i]->a[j]);
}
assert(i == n && parent_stack[i] == tree);
/* next, unwind stack until note_tree_consolidate() is done */
while (i > 0 &&
!note_tree_consolidate(parent_stack[i], parent_stack[i - 1],
GET_NIBBLE(i - 1, entry->key_sha1)))
i--;
}
/*
* Determine optimal on-disk fanout for this part of the notes tree
*
* Given a (sub)tree and the level in the internal tree structure, determine
* whether or not the given existing fanout should be expanded for this
* (sub)tree.
*
* Values of the 'fanout' variable:
* - 0: No fanout (all notes are stored directly in the root notes tree)
* - 1: 2/38 fanout
* - 2: 2/2/36 fanout
* - 3: 2/2/2/34 fanout
* etc.
*/
static unsigned char determine_fanout(struct int_node *tree, unsigned char n,
unsigned char fanout)
{
/*
* The following is a simple heuristic that works well in practice:
* For each even-numbered 16-tree level (remember that each on-disk
* fanout level corresponds to _two_ 16-tree levels), peek at all 16
* entries at that tree level. If all of them are either int_nodes or
* subtree entries, then there are likely plenty of notes below this
* level, so we return an incremented fanout.
*/
unsigned int i;
if ((n % 2) || (n > 2 * fanout))
return fanout;
for (i = 0; i < 16; i++) {
switch (GET_PTR_TYPE(tree->a[i])) {
case PTR_TYPE_SUBTREE:
case PTR_TYPE_INTERNAL:
continue;
default:
return fanout;
}
}
return fanout + 1;
}
/*
* To find a leaf_node:
* Search to the tree location appropriate for the given key:
* If a note entry with matching key, return the note entry, else return NULL.
*/
static struct leaf_node *note_tree_find(struct notes_tree *t,
struct int_node *tree, unsigned char n,
const unsigned char *key_sha1)
{
void **p = note_tree_search(t, &tree, &n, key_sha1);
if (GET_PTR_TYPE(*p) == PTR_TYPE_NOTE) {
struct leaf_node *l = (struct leaf_node *) CLR_PTR_TYPE(*p);
if (hasheq(key_sha1, l->key_oid.hash))
return l;
}
return NULL;
}
/* Free the entire notes data contained in the given tree */
static void note_tree_free(struct int_node *tree)
{
unsigned int i;
for (i = 0; i < 16; i++) {
void *p = tree->a[i];
switch (GET_PTR_TYPE(p)) {
case PTR_TYPE_INTERNAL:
note_tree_free(CLR_PTR_TYPE(p));
/* fall through */
case PTR_TYPE_NOTE:
case PTR_TYPE_SUBTREE:
free(CLR_PTR_TYPE(p));
}
}
}
/*
* How to consolidate an int_node:
* If there are > 1 non-NULL entries, give up and return non-zero.
* Otherwise replace the int_node at the given index in the given parent node
* with the only NOTE entry (or a NULL entry if no entries) from the given
* tree, and return 0.
*/
static int note_tree_consolidate(struct int_node *tree,
struct int_node *parent, unsigned char index)
{
unsigned int i;
void *p = NULL;
assert(tree && parent);
assert(CLR_PTR_TYPE(parent->a[index]) == tree);
for (i = 0; i < 16; i++) {
if (GET_PTR_TYPE(tree->a[i]) != PTR_TYPE_NULL) {
if (p) /* more than one entry */
return -2;
p = tree->a[i];
}
}
if (p && (GET_PTR_TYPE(p) != PTR_TYPE_NOTE))
return -2;
/* replace tree with p in parent[index] */
parent->a[index] = p;
free(tree);
return 0;
}
static int for_each_note_helper(struct notes_tree *t, struct int_node *tree,
unsigned char n, unsigned char fanout, int flags,
each_note_fn fn, void *cb_data)
{
unsigned int i;
void *p;
int ret = 0;
struct leaf_node *l;
static char path[FANOUT_PATH_MAX];
fanout = determine_fanout(tree, n, fanout);
for (i = 0; i < 16; i++) {
redo:
p = tree->a[i];
switch (GET_PTR_TYPE(p)) {
case PTR_TYPE_INTERNAL:
/* recurse into int_node */
ret = for_each_note_helper(t, CLR_PTR_TYPE(p), n + 1,
fanout, flags, fn, cb_data);
break;
case PTR_TYPE_SUBTREE:
l = (struct leaf_node *) CLR_PTR_TYPE(p);
/*
* Subtree entries in the note tree represent parts of
* the note tree that have not yet been explored. There
* is a direct relationship between subtree entries at
* level 'n' in the tree, and the 'fanout' variable:
* Subtree entries at level 'n <= 2 * fanout' should be
* preserved, since they correspond exactly to a fanout
* directory in the on-disk structure. However, subtree
* entries at level 'n > 2 * fanout' should NOT be
* preserved, but rather consolidated into the above
* notes tree level. We achieve this by unconditionally
* unpacking subtree entries that exist below the
* threshold level at 'n = 2 * fanout'.
*/
if (n <= 2 * fanout &&
flags & FOR_EACH_NOTE_YIELD_SUBTREES) {
/* invoke callback with subtree */
unsigned int path_len =
l->key_oid.hash[KEY_INDEX] * 2 + fanout;
assert(path_len < FANOUT_PATH_MAX - 1);
construct_path_with_fanout(l->key_oid.hash,
fanout,
path);
/* Create trailing slash, if needed */
if (path[path_len - 1] != '/')
path[path_len++] = '/';
path[path_len] = '\0';
ret = fn(&l->key_oid, &l->val_oid,
path,
cb_data);
}
if (n > fanout * 2 ||
!(flags & FOR_EACH_NOTE_DONT_UNPACK_SUBTREES)) {
/* unpack subtree and resume traversal */
tree->a[i] = NULL;
load_subtree(t, l, tree, n);
free(l);
goto redo;
}
break;
case PTR_TYPE_NOTE:
l = (struct leaf_node *) CLR_PTR_TYPE(p);
construct_path_with_fanout(l->key_oid.hash, fanout,
path);
ret = fn(&l->key_oid, &l->val_oid, path,
cb_data);
break;
}
if (ret)
return ret;
}
return 0;
}
/*
* To insert a leaf_node:
* Search to the tree location appropriate for the given leaf_node's key:
* - If location is unused (NULL), store the tweaked pointer directly there
* - If location holds a note entry that matches the note-to-be-inserted, then
* combine the two notes (by calling the given combine_notes function).
* - If location holds a note entry that matches the subtree-to-be-inserted,
* then unpack the subtree-to-be-inserted into the location.
* - If location holds a matching subtree entry, unpack the subtree at that
* location, and restart the insert operation from that level.
* - Else, create a new int_node, holding both the node-at-location and the
* node-to-be-inserted, and store the new int_node into the location.
*/
static int note_tree_insert(struct notes_tree *t, struct int_node *tree,
unsigned char n, struct leaf_node *entry, unsigned char type,
combine_notes_fn combine_notes)
{
struct int_node *new_node;
struct leaf_node *l;
void **p = note_tree_search(t, &tree, &n, entry->key_oid.hash);
int ret = 0;
assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
l = (struct leaf_node *) CLR_PTR_TYPE(*p);
switch (GET_PTR_TYPE(*p)) {
case PTR_TYPE_NULL:
assert(!*p);
if (is_null_oid(&entry->val_oid))
free(entry);
else
*p = SET_PTR_TYPE(entry, type);
return 0;
case PTR_TYPE_NOTE:
switch (type) {
case PTR_TYPE_NOTE:
if (oideq(&l->key_oid, &entry->key_oid)) {
/* skip concatenation if l == entry */
if (oideq(&l->val_oid, &entry->val_oid))
return 0;
ret = combine_notes(&l->val_oid,
&entry->val_oid);
if (!ret && is_null_oid(&l->val_oid))
note_tree_remove(t, tree, n, entry);
free(entry);
return ret;
}
break;
case PTR_TYPE_SUBTREE:
if (!SUBTREE_SHA1_PREFIXCMP(l->key_oid.hash,
entry->key_oid.hash)) {
/* unpack 'entry' */
load_subtree(t, entry, tree, n);
free(entry);
return 0;
}
break;
}
break;
case PTR_TYPE_SUBTREE:
if (!SUBTREE_SHA1_PREFIXCMP(entry->key_oid.hash, l->key_oid.hash)) {
/* unpack 'l' and restart insert */
*p = NULL;
load_subtree(t, l, tree, n);
free(l);
return note_tree_insert(t, tree, n, entry, type,
combine_notes);
}
break;
}
/* non-matching leaf_node */
assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
if (is_null_oid(&entry->val_oid)) { /* skip insertion of empty note */
free(entry);
return 0;
}
new_node = (struct int_node *) xcalloc(1, sizeof(struct int_node));
ret = note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
combine_notes);
if (ret)
return ret;
*p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
return note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
}
/*
* To insert a leaf_node:
* Search to the tree location appropriate for the given leaf_node's key:
* - If location is unused (NULL), store the tweaked pointer directly there
* - If location holds a note entry that matches the note-to-be-inserted, then
* combine the two notes (by calling the given combine_notes function).
* - If location holds a note entry that matches the subtree-to-be-inserted,
* then unpack the subtree-to-be-inserted into the location.
* - If location holds a matching subtree entry, unpack the subtree at that
* location, and restart the insert operation from that level.
* - Else, create a new int_node, holding both the node-at-location and the
* node-to-be-inserted, and store the new int_node into the location.
*/
static void note_tree_insert(struct notes_tree *t, struct int_node *tree,
unsigned char n, struct leaf_node *entry, unsigned char type,
combine_notes_fn combine_notes)
{
struct int_node *new_node;
struct leaf_node *l;
void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
l = (struct leaf_node *) CLR_PTR_TYPE(*p);
switch (GET_PTR_TYPE(*p)) {
case PTR_TYPE_NULL:
assert(!*p);
*p = SET_PTR_TYPE(entry, type);
return;
case PTR_TYPE_NOTE:
switch (type) {
case PTR_TYPE_NOTE:
if (!hashcmp(l->key_sha1, entry->key_sha1)) {
/* skip concatenation if l == entry */
if (!hashcmp(l->val_sha1, entry->val_sha1))
return;
if (combine_notes(l->val_sha1, entry->val_sha1))
die("failed to combine notes %s and %s"
" for object %s",
sha1_to_hex(l->val_sha1),
sha1_to_hex(entry->val_sha1),
sha1_to_hex(l->key_sha1));
free(entry);
return;
}
break;
case PTR_TYPE_SUBTREE:
if (!SUBTREE_SHA1_PREFIXCMP(l->key_sha1,
entry->key_sha1)) {
/* unpack 'entry' */
load_subtree(t, entry, tree, n);
free(entry);
return;
}
break;
}
break;
case PTR_TYPE_SUBTREE:
if (!SUBTREE_SHA1_PREFIXCMP(entry->key_sha1, l->key_sha1)) {
/* unpack 'l' and restart insert */
*p = NULL;
load_subtree(t, l, tree, n);
free(l);
note_tree_insert(t, tree, n, entry, type,
combine_notes);
return;
}
break;
}
/* non-matching leaf_node */
assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
combine_notes);
*p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
}
